Contact lens cleaning and storing composition including nonionic surfactant, benzalkonium chloride and Na{hd 3{b EDTA

ABSTRACT

A contact lens cleaning, storing and wetting solution is provided for cleaning, storing and wetting flexible silicone contact lenses. The solution comprises a poly(oxyethylene)poly(oxypropylene) block copolymer having a molecular weight between about 1,900 and 15,500, a water solubility in excess of about 10 grams per 100 ml., a cloud point in 1% aqueous solution above about 30*C., and a Foam Height in excess of 30 mm; a microbial growth inhibitor, such as benzalkonium chloride; purified water; and a sufficient amount of at least one essentially neutral, water-soluble compatible salt to provide a solution salt content equivalent to about 0.5 to 1.8% sodium chloride. The solution can also contain disodium or trisodium ethylenediamine tetraacetate and a polymeric viscosity building agent, if desired. A cleaning composition for polyhydroxylated alkyl methacrylate soft contact lenses includes the above poly (oxyethylene)poly(oxypropylene) block copolymer and sorbic acid as a germicidal ingredient.

United States Patent [1 1 Krezanoski et al.

[451 May6,1975

[75] Inventors: Joseph Z. Krezanoski; John C.

Petricciani, both of Los Altos, Calif.

[73] Assignee: Flow Pharmaceuticals, Inc., Palo Alto, Calif.

22 Filed: Aug.11,1972

211 App]. No.: 279,800

Related U.S. Application Data [63] Continuation-impart of Ser. No. M8993, June I, l97l, abandoned, which is a continuation-impart of Ser. No. 724,600, April 26, I968, abandoned.

[S2] U.S. Cl. 252/106; 424/78; 424/329; 252/DIG. l [51] Int. Cl. Clld U66; Cl 1d 3/48 [58] Field of Search 252/l06, 107, DIG. I; 424/78, 329

[56] References Cited UNITED STATES PATENTS 2,703,777 3/1955 Feinstein et al. 424/329 X OTHER PUBLICATIONS Rose et al. The Condensed Chemical Dictionary, 7th

Ed., p. I05, Reinhold Publishing Corporation, (1966) New York.

Sequestrene," Technical Bulletin, Wyandote Chemical Co., Wyandotte, Michigan, pp. 13. 25 & 26, (1954).

Primary Examiner-Benjamin R. Padgett Assistant Examiner-E. A. Miller Attorney, Agent, or FirmFinnegan, Henderson, Farabow & Garrett [57] ABSTRACT A contact lens cleaning, storing and wetting solution is provided for cleaning, storing and wetting flexible silicone contact lenses. The solution comprises a poly- (oxyethylene)- poly(oxypropylene) block copolymer having a molecular weight between about 1,900 and l5,500, a water solubility in excess of about 10 grams per 100 ml., a cloud point in l% aqueous solution above about 30C., and a Foam Height in excess of 30 mm; a microbial growth inhibitor, such as benzalkonium chloride; purified water; and a sufficient amount of at least one essentially neutral, water-soluble compatible salt to provide a solution salt content equivalent to about 0.5 to 1.8% sodium chloride. The solution can also contain disodium or trisodium ethylenediamine tetraacetate and a polymeric viscosity building agent, if desired.

A cleaning composition for polyhydroxylated alkyl methacrylate soft contact lenses includes the above poly (oxyethylene)- poly(oxypropylene) block copolymer and sorbic acid as a germicidal ingredient.

11 Claims, No Drawings CONTACT LENS CLEANING AND STORING COMPOSITION INCLUDING NONIONIC SURFACTANT, BENZALKONIUM CHLORIDE AND NA EDTA This application is a continuation-in-part of application Ser. No. 148,993, filed June 1, I971, entitled CLEANING AND GERMICIDAL COMPOSITIONS now abandoned, which is a continuation-in-part of application Ser. No. 724,600, filed Apr. 26, I968 entitled CLEANING AND GERMICIDAL COMPOSITIONS, now abandoned.

This invention relates to various contact lens cleaning, storing and wetting compositions, and more particularly to compositions for treating soft contact lenses, such as flexible silicone contact lenses and polyhydroxylated alkyl methacrylate contact lenses, and to com positions for use with conventional hard polymethylmethacrylate lenses.

The proper care of contact lenses can be viewed as requiring three necessary steps. First, after removal from the eye the lenses must be cleaned to physically remove foreign matter from their surfaces. Second, the lenses must be sterilized. Finally, the lenses must be prepared for insertion into the eye.

In the past, contact lenses have been made of hard polymethacrylates. Proper care of these lenses has required that they be stored in specially developed cleaning and storage solutions to maintain them in good order when not in use. The storage solutions are formulated to sterilize the lenses during the lensess storage. Many of these cleaning and storage solutions contain chlorobutanol as a preservative which acts to preserve the sterility of the solution.

When ready for use, the hard contact lenses have been immersed in contact lens wetting solutions. The wetting solutions are designed to condition and prepare the contact lenses for wetting by natural tear fluid, and their use has made the wearing of contact lenses more tolerable, particularly in the newly initiated patient, by reducing irritation of the corneal epithelium. Prior art contact lens wetting solutions have usually contained polyvinyl alcohol as a wetting agent. These wetting solutions also have often contained chlorobutanol as a preservative.

Recently, a new type of contact lens known as a soft lens has been developed. Soft lenses can be divided into two broad catagories, namely hydrophilic lenses and hydrophobic lenses. The care of each of these lenses presents special and different problems.

Hydrophobic contact lenses are usually based on elastic and flexible silicone rubber (polysiloxane), and are generally made from cross-linked dimethyl polysiloxane which is commonly known as Antifoam A. A typical preparation of a hydrophobic silicone contact lens is disclosed in US. Pat. No. 3,228,741, which is hereby incorporated by reference and comprises forming a mixture of a suitable polymerization catalyst, up to 40% silica as a filler, and the siloxane polymer, and then molding and during with heat to further polymerize the polysiloxane by cross-linking to produce the finished clear lens. Clinical testing of flexible silicone rubber lenses has created a need for cleaning, storing and wetting solutions that can be effectively used with these lenses.

In testing the commercially available solutions designed for conventional hard polymethylmethacrylate contact lenses, it has been found that they are not adequate and in some instances detrimental to the successful use of flexible silicone contact lenses. For example, it has been found that polyvinyl alcohol, the wetting ingredient in many wetting solutions for conventional hard polymethylmethacrylate lenses, is not an effective wetting agent for silicone lenses. It has also been found that the preservative chlorobutanol present in many commercially available solutions designed for hard polymethylmethacrylate lenses is adsorbed and concentrated by silicone lenses. This ability of the silicone elastomer to concentrate chlorobutanol could ultimately change the physical and chemical properties of the lenses to make them ineffective in providing visual correction.

Moreover, patients, experimentally wearing flexible silicone rubber lenses stored in a chlorobutanol containing storage solution have complained of discomfort. This was found to be directly associated with the high concentrations of chlorobutanol in the silicone lenses thus treated.

The highly hydrophobic nature of the silicone elasto mer has prevented their uniform and effective cleaning and wetting by all available conventional cleaners and wetting agents. Thus, various generic classes of organic compounds have been screened including cellulose derived gums, polyvinylpyrrolidone polymers, polyvinyl alcohol with varying degrees of acetylation, polysaccharides, lanolin derived nonionic surfactants, ethoxylated sorbitol anhydrides, and various cationic, anionic and nonionic detergents, but to date none have been found acceptable.

Hydrophilic soft contact lenses are hydrated gel lenses which can be prepared by copolymerizing hydrophilic organic monomers having an olefmic double bond with a small amount of a crosslinking agent usually having two polymerizable, olefinic double bonds. These lenses are usually based on polyhydroxylated alkyl methacrylates and contain a polyhydroxylated alkyl methacrylate, such as polyhydroxyethyl methacrylate, cross-linked with, for example, a hydroxyethyl dimethacrylate. Usually, there is about one (I) crosslinking molecule for every 200 monomer units. By comparison, the conventional hard contact lens consists of polymethylmethacrylate cross-linked with hydroxyethyl dimethacrylate. The absence of a hydrophilic OH group in conventional hard lenses accounts for the tremendous difference in behavior of the two materials.

Hydrated gel lenses can contain the following materials: (I) hydroxyethylmethacrylate (HEMA) or its analogues, (2) ethylene-glycol dimethacrylate (EGMA) or its analogues. (3) polymethylmethacrylate (PMMA) or its analogues, (4) polyvinylpyrrolidone (PVP), (5) traces of the respective monomers, (6) traces of inhibitors such as hydroquinine, (7) traces of catalysts such as benzyl peroxide, and (8) water. A more detailed de scription of hydrated gel lenses is found in U. S. Pat. Nos. 2,976,576; 3,220,960; 3,361,858; 3,408,429; 3,496,254; and 3,499,862, which patents are hereby incorporated by reference.

Soft contact lenses of the hydrated gel type have a number of properties which complicate their effective care. For example, the hydrophilic OH groups of the lenses attract and hold large amounts of water in the plastic, and this leads to difficulties in cleaning and sterilizing the lenses. Further difficulties in caring for hydrated gel lenses occur because these lenses complex and concentrate chlorobutanol, benzalkonium chloride, thimerosal, phenylmercuric nitrate and other preservatives found in solutions for conventional lenses. Generally, these preservatives are inactivated in the complexed state. Also, if concentrated preservatives are released too rapidly at the cornea, they may cause chemical burns. Thus, solutions and cleaners now available for conventional hard lenses cannot be used with gel lenses.

The methods currently used in caring for hydrophilic gel lenses generally include the following: 1 boiling in saline; 2) treating with 3% hydrogen peroxide; 3) rinsing with sterile saline; and 4) storing in sterilizing so' lutions. Each of these methods, however. have numerous disadvantages. For example, boiling in saline kills pathogens, but does not kill spores. Another disadvantage of boiling is that it is not convenient for patients to carry the boiling devices with them wherever they go. Further. proteins and other materials may be denatured and deposited on or in the lens matrix if the lenses are not adequately cleaned prior to boiling. The effects of boiling on soluble or water dispersible proteins are similar to the coagulating and insolubilizing effects of heat on egg whites. Thus, once these deposits are allowed to accumulate on the lenses, substantially more effort is required to clean them.

Commercial hydrogen peroxide has satisfactory germicidal activity, but its use also has a number of disadvantages. Commercial hydrogen peroxide has a pH of about 3 and it is therefore necessary to treat the lenses with sodium bicarbonate solution to neutralize the high acidity before the lenses can be worn safelyv A major concern, however, is the ever present possibility that the patient will forget to neutralize and dilute the hydrogen peroxide with sodium bicarbonate solution prior to inserting the lens. Further, the cleaning action of hydrogen peroxide is not better than that achieved with water or isotonic salt solutions. In fact, hydrogen peroxide, because of its oxidative chemical reactivity, can denature and precipitate proteins.

Rinsing lenses with unpreserved and supposed sterile saline solution delivered from a large multiple dose bot tle, is far from adequate in sterilizing lenses.

Experimental isotonic sterilizing solutions of two basic types are currently available. One solution contains chlorhexidine gluconate 0.005% as the active in gredient. Another solution contains 0.001% thimerosal, 0.05% EDTA, and chlorhexidine 0.005%. Both of these solutions have drawbacks. Thus, chlorhexidine is not only inactivated by many peptides, proteins and fatty substances of natural origin bearing a net negative charge, but causes the formation of insoluble precipitates. To a lesser extent, this same phenomenon may occur when the negatively charged thimerosal ion reacts with proteins bearing a net positive charge. Further, neither solution is idea] when prolonged wearing comfort, complete sterility reliance and lack of allergic response are considered. Although these solutions have been tested for their cleaning efficiency, they fall significantly short of accomplishing this objective when used on a routine basis. This is not surprising since neither of these solutions was specifically formulated for this purpose.

The necessity for proper cleaning of the new hydrophilic gel lenses is readily apparent. Throughout the development phase of these lenses, there has been no ef fective preparation in clinical testing and none has been formulated or developed specifically for routine cleaning of gel lenses.

Any residual protein remaining in or on the lens may readily inactivate even the best germicidal agents and serve as growth medium for a variety of microorganisms. While many germicidal chemicals, in appropriate concentrations, demonstrate sterilization of fresh lenses, these same chemicals do not necessarily sterilize a lens worn repeatedly and improperly cleaned. Thus, there is a continuing need for an effective cleaner for hydrated gel lenses which would permit the lenses to be cleaned before they are placed in a germicidal environment to minimize the likelihood of overwhelming the germicide.

It has now been found that certain members of the polyoxypropylene-polyoxyethylene class of block copolymers are effective in accomplishing both cleaning, storing and wetting of flexible silicone lenses and that these same members in combination with sorbic acid as a preservative are effective in providing cleaning of hydrophilic gel lenses.

Accordingly, the present invention provides a sterile, aqueous cleaning, storing and wetting solution for flexible silicone rubber contact lenses containing as the active wetting and cleaning ingredient 0.0l 30% of a polyoxyethylene -polyoxypropylene block copolymer having a molecular weight between about [,900 and I5, 500, a water solubility in excess of about 10 grams per ml., a cloud point in a 1% aqueous solution above about 30C, and a Foam Height in excess of 30 mm. The solution also contains a sufficient amount of a germicidal composition compatible with silicone lenses to preserve the sterility of the solution; a sufficient amount of at least one water-soluble, compatible salt to provide a solution salt content equivalent to about 0.5 to 1.8% sodium chloride, and balance water.

The above composition for cleaning, storing and wet ting flexible silicone rubber lenses can contain a viscosity builder such as hydroxyethyl cellulose and this combination of ingredients provides an all purpose composition for cleaning, storing and wetting conventional hard, polymethacrylate lenses.

The present invention also provides a new cleaning composition for hydrated gel lenses which comprises 001 to 40% of a polyoxyethylenepolyoxypropylene block copolymer having a molecular weight between about 1,900 and l5. 500, a water solubility in excess of about 10 grams per 100 ml, a cloud point in a l aqueous soiution above about 30C, a Foam Height in excess of 30 mm, and sorbic acid as a germicidal ingredient to preserve the sterility of the composition. The composition also includes a sufficient amount of at least one water soluble compatible salt to provide a solution having having a tonicity compatible with human tear fluid, and a balance of water. This cleaning composition can also be used to clean conventional hard polymethacrylate lenses and flexible silicone rubber soft contact lenses.

The invention consists in the novel compositions, methods, products and improvements shown and described. it is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory but are not restrictive of the invention.

The silicone lens cleaning, storing and wetting solution of this invention is an aqueous solution. The inert nature of water. and the fact that it is a good solvent for the other ingredients of the present solution, together with its ready availability make it the desirable base material for this solution. The water used in the solution is preferably purified by distillation, filtration, ionexchange or the like.

The silicone lens cleaning, storing and wetting solution of this invention preferably contains a compatible, polymeric, viscosity-building agent. The viscositybuilding agent must, of course, be water soluble. Either cellulosic polymers or natural gums are satisfactory viscosity-building agents for the solutions.

Thus, natural gums such as guar gum, gum tragacanth, gelatin and water-soluble starch derivatives can be used. Water-soluble cellulosic polymers such as hydroxyethyl cellulose, methyl cellulose, hydroxypropyl cellulose, carboxymethyl cellulose, and the like are preferred viscosity-building agents, with hydroxyethyl cellulose and methyl cellulose being considered optimum.

The viscosity-building agent used in the solution of this invention provides lens cushioning and corneal comfort, while avoiding stickiness of the eyelid and granulation on the eyelashes. These desirable properties are best achieved through the use of hydroxyethyl cellulose or methyl cellulose as the viscosity-building agents.

Sufficient amounts of the viscosity-building agent are added to the solution to produce a cleaning and wetting solution having a viscosity of about to 750 cps at 25C. A viscosity of about 60 cps at 25C is considered optimum.

The use of medium viscosity cellulosic polymers, which are readily available commercially, is beneficial in achieving the desired viscosity in the silicone rubber contact lens cleaning, storing and wetting solution. Exemplary of such medium viscosity polymers are M grade hydroxyethyl cellulose available from Hercules, lnc., under the trademark Natrosol. A 2% solution of this polymer at 25C has a Brookfield viscosity of about 4,500-6,500. It is to be understood, however, that cellulosic polymers of widely varying viscosities can be used satisfactorily in the wetting solutions of this inven tion. Thus, Natrosol polymers of viscosity grades H, G and J from Hercules, Cellosize W 1 4,400 from Union Carbide Corp. and various other commercially available hydroxyethyl cellulose polymers can be used. The preferred grade of methyl cellulose for use in these cleaning and wetting solutions is methyl cellulose U.S.P. XVll, which can be obtained commercially from Dow Chemical Co., Union Carbide and others.

Highly desirable silicone contact lens cleaning, storing and wetting solutions are produced by the incorporation of 0.05 to 1.0% of the viscosity-building agents in the solution.

The silicone rubber contact lens cleaning, storing and wetting solution of this invention contains a germicide, designed to prevent or inhibit microbial growth. The inclusion of such germicides is particularly important where multi-dose bottles of the solution are prepared. The germicides prevent bacteria from contaminating the solution after its container has been opened and ini tial use made of a portion of the solution. The germicidal ingredient used in the silicone lens treating composition of this invention is bactericidal and imparts a sterilizing capability to the composition so that it can be used as a soaking solution for contact lens storage.

Quaternary germicides are preferred, particularly benzalkonium chloride. This compound has minimal potential for toxicity and irritation at the germicidally effective strengths incorporated in the present solution, and it does not present a significant problem of percutaneous absorption. Benzalkonium chloride is an alkyl substituted dimethylybenzylammonium chloride in which the alkyl substituents are a mixture of C to C alkyl radicals.

Other well known germicidal agents compatible with flexible silicone lenses such as thimerosal sodium, cetylpyridinium chloride, and benzethonium chloride can be substituted wholly or partially for the preferred benzalkonium chloride preservative. Sorbic acid, NF Xll can also be used as a germicidal ingredient in the silicone lens solution of this invention. In order to maintain sterility of the product during use, the preferred quaternary or organic mercurial germicide should be present in an amount of about 0.001 to 0.03% of the overall solution, and preferably in concentrations of from 0.004 to 0.02% The optimum concentration is about 0.01%. A preferred concentration for sorbic acid NF XIII is between about 0.0l and 0.5% of the overall solution.

The silicone contact lens cleaning, storing and wetting solution of this invention can optionally contain about 0.01 to 2% of a salt of ethylenediaminetetraacetic acid, and preferably contains disodium or trisodium ethylenediaminetetraacetate. The former is commonly known as sodium edetate.

Trisodium edetate serves as a combination germicide and chelating agent and its inclusion in the present composition at levels of 0.01 to 2% maintains the pH of the composition at alkaline levels, i.e., above pH 7.0, and preferably at from pH 8 to 9. The alkalinity of the solution enhances the germicidal activity of quaternary germicides such as benzalkonium chloride, and also enhances the solvent activity of the composition for proteins, fats, and mucopolysaccharides that accumulate on the plastic surfaces of contact lenses from contact with body tissues and fluids during normal use.

Specifically, trisodium ethylenediaminetetraacetate enhances the germicidal action of benzalkonium chloride against certain gram negative organisms including Pseudomonas aeruginosu, Alcaligenese faec'ulis. and Escherichia coli. The enhancement of germicidal activity is particularly significant in the alkaline environment.

The alkalinity of the compositions of this invention produced by the use of trisodium ethylenediaminetetraacetate also improves the chelating ability and therefore the water softening characteristics of the trisodium ethylenediaminetetraacetate, a property that is desirable in a cleaning and germicidal composition for contact lenses. These chelating and water softening properties of the solution are important because divalent and trivalent cations often present in body fluids can reduce the germicidal potency of benzalkonium chloride by blocking the surfaces of the lenses to be cleaned.

Disodium ethylenediamine tetraacetate also provides additional protection against pseudomonal contamination. and also acts as a chelating or water softening agent. The sodium edetate ties up divalent and trivalent cations often present in the water, thereby preventing undesirable precipitates from forming and ultimately fogging the contact lens surface. Other salts of ethylenediaminetetraacetate, such as the dipotassium salt can be used in the present invention.

The silicone rubber contact lens cleaning, storing and wetting solutions of this invention preferably have a pH between about and 9. The solutions are not buffered, however, and therefore do not resist conversion to a normal pH by tear fluid which usually has a pH of about 7.4. The elimination of buffers from the present solution is desirable because strongly buffered solutions can cause temporary stinging and discomfort of the eye on contact with the solution or a contact lens wetted with it.

A sufficient amount of at least one essentially neutral water-soluble compatible salt is incorporated in the silicone lens treating solutions of this invention to provide a solution salt content equivalent to about 0.5 to 1.8% sodium chloride. The silicone contact lens cleaning, storing and wetting solutions of the present invention are generally formulated to be isotonic with human serum and tear fluid, that is, they are formulated to contain the same salt concentration as that present in the serum and tear fluid of the user. The normal tonicity of human serum and tear fluid is 0.9% (9.0 grams of sodium chloride per liter of fluid), and normally, isotonic solutions contain approximately 0.9% sodium chloride, or other salt or mixture of salts having a tonicity approximately equivalent to that of 0.9% sodium chloride.

The tonicity of the solution, however, can be as low as 0.5 or as high as 1.8. Thus, it is sometimes desirable to provide a mildly hypertonic silicone lens cleaning, storing and wetting solution. that is, a solution having a salt concentration and hence an osmotic pressure higher than that of the serum and tear fluid of the contact lens wearer. Mildly hypertonic solutions can be used in the present invention, and the teachings of U.S. Pat. No. 3,549,747 relating to the formulation of such solutions are hereby incorporated by reference. Thus, the silicone lens treating solutions of the present inven tion can have a tonicity equivalent to about 1.5% so dium chloride as taught in US. Pat. No. 3,549.747 and can have a maximum tonicity equivalent to about 1.8% sodium chloride.

As will be apparent to those of ordinary skill in the art any soluble salt or mixture of salts compatible with ocular tissue can be used to provide the desired tonicity. Preferably, sodium chloride, potassium chloride, or mixtures thereof, are used to provide the desired tonicity. It is to be understood, however, that one or more essentially netural, water soluble alkali metal salts can be substituted in whole or in part for the sodium or potassium chloride in the solutions of this invention. Thus, other alkali metal halides, such as sodium bromide, potassium fluoride or potassium bromide can be used. Other salts, such as sodium sulfate, potassium sulfate, sodium nitrate, sodium phosphate, potassium nitrate or potassium phosphate can also be used. The tonicity of the silicone lens treating solutions of this invention however, is stated in terms of sodium chloride, and when such other salts are used, they should be present in amounts equivalent to the tonicity of about 0.5 to 1.8% sodium chloride solutions.

In accordance with the invention, the silicone lens treating composition contains a physiologicallyacceptable and chemically compatible polyoxpropylene-polyoxyethylene block copolymer. This copolymer is the primary wetting and cleaning ingredient of the compoosition.

The products sold under the trademark Pluronic by Wyandotte Chemical Corp. are a series of closely related block polymers that may be generically classified as polyoxypropylene-polyoxyethylene condensates terminating in primary hydroxyl groups. They are formed by the condensation of propylene oxide onto a propylene glycol nucleus followed by the condensation of ethylene oxide onto both ends of the polyoxypropylene base. The polyoxyethylene hydrophilic groups on the ends of the molecule are controlled in length to constitute anywhere from 10% to by weight of the final molecule. This series of products may be represented empirically by the formula:

llO((lll Cl 120) (Cl lCl 1 0) (C]l Cll O)cll where a and c are statistically equal. These polyol block copolymers are nonionic surface -active agents.

In accordance with the invention, certain members of this series of block polymers having a particular combination of physical and chemical properties have been found to be effective cleaning and wetting agents for flexible silicone contact lenses. Thus, the polyoxypropylene-polyoxyethylene block copolymers useful in the present invention have a molecular weight between about 1,900 and 15,500, and a water solubility is in excess of about 10 grams per ml.

Additionally, the block copolymers useful in the present invention must have a cloud point in l aqueous solution above about 30C, and a Foam Height in excess of 30 mm. The cloud point is the temperature at which as waxy solid material appears in solutions as a 1% aqueous solution of the block copolymer is cooled. The Foam Height is the value obtained on a Dynamic Foam Tester operated at a temperature of F using a 0.1% polyol concentration at a flow rate of 400 mL/min. for ten minutes.

An additional requirement of the block copolymers used in the silicone lens treating solution of the present invention is that they be physiologica1ly-acceptable so that no adverse reaction occurs when the solution comes in contact with human tissue or fluids. Thus, aqueous solutions of the block copolymers must be inert when they are tested for ocular tolerance in human and rabbit eyes.

Among the polyoxypropylene-polyoxyethylene block copolymers satisfying the above conditions are the following Pluronic copolymers: Pluronic F-68, Pluronic L-44, Pluronic L-62, Pluronic L-64, Pluronic F-l08, and Pluronic F-l 27. Pluronics F-68, L-44, L-62, L-64, lF-l08 and F-l27 when tested in concentrations of 10% 25% show only minimal or no eye irritation. The following Table 1 lists the properties of a number of the block copolymers that can be used in the present invention.

TABLE I Average (loud Point Solubility FOAMING PROPERTIES PLURONIC Molecular in W1 Au. in Foam Heights (mm! Weight Solution. T, Water at flow of 400 ml/min.

l) L44 2200 65 l 300 2) L62 2500 32 l0 35 3) L64 2900 58 Ill 600 H1 63 8350 l()(| ll] 600 5) FlOX l5,5l][l l()(] It] 435 6) H27 11,500 l()(| |0 250 To perform the important dual cleaning and wetting functions of the silicone lens treating solutions of this invention, the block copolymers should be present in an amount of from 0.01 to 30 percent of the solution, and preferably are present in an amount of 0.01% to 5% of the solution. At these concentrations, the block copolymers effectively remove proteins, fats, and mucopolysaccharides that accumulate on the silicone lens surfaces when they come in contact with body tissues and fluids. The block copolymers also act to help maintain the germicidal storage container in a generally clean state. importantly, the block copolymers also act as a wetting agent in the solution so that the flexible silicone contact lenses can be immediately inserted in the eye of the user upon their removal from the solution without using a separate wetting solution.

The silicone lens treating solutions of the present invention are thus used for cleaning, storing, wetting and preconditioning flexible silicone contact lenses and make these lenses a safe and functional prosthesis for correcting visual abberations.

When the above compositions for cleaning, storing and wetting silicone lenses contain a viscosity builder, such as hydroxyethyl cellulose, they also have utility as an all purpose solution for cleaning, storing and Wetting conventional hard polymethacrylate lenses in addition to the above all-purpose compositions for cleaning, storing and wetting conventional hard polymethacrylate lenses, this invention also provides still other cleaning and germicidal compositions for the conventional hard lenses. These cleaning compositions consist essentially of (a) from 0,002 to 0.2% benzalkonium chloride for inhibiting microbial growth in the composition (b) from 0.0] to 2% trisodium ethylenediaminetetraacetate (c) a physiologically acceptable nonionic surfactant selected from the group consisting of polyoxyethylene fatty acid ethers, polyoxyethylene fatty acid esters and polyoxypropylenepolyoxyethylene block polymers, and (d) water.

The cleaning and germicidal composition for hard contact lenses contains benzalkonium chloride as a quaternary germicide which acts to inhibit or prevent microbial growth. The germicidal activity of this preservative ingredient is enhanced by the action of the other compounds present in the solution. in order to effectively sterilize hard contact lenses, the cleaning compositions of this invention desirably contain about 0.002 to 0.03% benzalkonium chloride, based on the overall composition and preferably contain this germicidal agent in concentrations of from 0.004 to 0.02%.

Trisodium ethylenediaminetetraacetate is incorporated in this hard contact lens treating composition of the invention as a combination germicide and chelating agent and maintains the pH of the composition at alkaline levels, i.e., above pH 7.0, and preferably at from 8 to 10. The alkalinity of the solution enhances the solvent activity of the composition for proteins, fats and mucopolysaccharides that accumulate on plastic surfaces of hard contact lenses from contact with body tissues and fluids during normal use, and enhances the germicidal action of benzalkonium chloride against certain gram negative organisms including Pseudomonas aeruginosa, Alcaligenese faecalis, and Escherichia coli. The enhancement of germicidal activity is particularly significant in the alkaline environment. The alka linity of the compositions of this invention produced by the use of trisodium ethylenediaminetatraacetate also improves the chelating ability and therefore the water softening characteristics of the trisodium ethylenediaminetatraacetate, a property that is desirable for a cleaning and germicidal composition for hard contact lenses.

The inclusion of a nonionic surfactant in this hard contact lens treating composition obviates the need for a separate cleaning operation and avoids the need for use of anionic detergents. Elimination of the use of anionic detergents, prior to cold sterilization treatment, insures that no residual amount of anionic detergent will remain on the plastic surface of the medical devices being sterilized. Thus, there can be no complex salt formation of the germicides of the present composition and attendant reduction in their germidical activity. Nonionic detergents that can be employed in the hard lens treating compositions of this invention include polyoxyethylene fatty acid ethers having a molec ular weight of from 300 to 4,000, polyoxyethylene fatty acid esters having a molecular weight of 350 to 4,500, and polyoxypropylene-polyoxyethylene block polymers having a molecular weight from 1,000 to l5,000. Exemplary of commercially available nonionic surfactants that can be used are Tween 80, 60, and 20, manufactured by the Atlas Powder Company (polyoxyalkylene derivatives of long chain fatty acid partial esters of hexitol anhydride); the lower molecular weight Pluronic surfactants; and the Span series of surface active agents manufactured by the Atlas Powder Company (long chain fatty acid partial esters of hexitol anhydrides including sorbitan, sorbides, manitans, and manides).

These hard lens treating compositions can take the form of an aqueous cleaning and storage solution, or a gel-form cleaning composition depending upon the type and amount of nonionic surfactant incorporated into the composition. The aqueous solutions are capable of serving as both a cleaning and a germicidal storage solution, while ordinarily the gel composition is utilized primarily as a cleaning composition and is usually rinsed from the lenses shortly after application.

For a wearer of hard contact lenses, a typical regimen would call for cleaning the lenses two to ten times a week using the gel-form cleaning composition which would be followed by water rinsing of the lenses. An important advantage of the gel-form cleaner is the ease with which it can be rinsed off the lenses using cold water. After a cleaning operation, if the lenses are not used immediately, the lenses would be stored in the cleaning and storage composition normally utilized. If the lenses are to be worn immediately, a wetting solution is applied to the cleaned and rinsed lenses before insertion by the wearer,

To perform the important cleaning function of the solutions of this invention, the nonionic surface active agent should be present in an amount of from 0.1 to percent of the solution. At these concentrations. the nonionic cleaning agent effectively removes proteins, fats, and mucopolysaccharides that accumulate on plastic surfaces when they come in contact with body tissues and fluids. The nonionic surface active agent also acts to help maintain the germicidal storage container in a generally clean state.

The gel-form cleaning composition contains a physiologically-acceptable nonionic surfactant at concentration levels that will provide a gel consistency at room temperature of 25C. The concentration of nonionic surfactant in the gel-form cleaning composition may vary from about 18-60%. In a preferred embodiment of the gel-form cleaning composition, the nonionic agent is a polyoxypropylene-polyoxyethylene block polymer having a molecular weight of about 1 1,500 containing about 70 percent by weight of poly- (oxyethylene) and sold under the trademark Pluronic F127 by the Wyandotte Chemical Corp. This pre ferred nonionic surfactant forms desirable gel compositions at levels of from above about 18 percent up to 30 percent with a 20 percent concentration being pres ently preferred. Other polyoxypropylenepolyoxyethylene block polymers having a molecular weight above 1450 and containing over 40 percent poly(oxyethylene) will form gels at higher surfactant concentrations. A preferred gel form cleaning composition for hard contact lenses consists essentially of 0.025% benzalkonium chloride; 0.25% trisodium ethylenedia minetetraacetate, 20% polyoxyproplenepolyoxyethylene block copolymers having a molecular weight of from 10,500 to 12,500, and purified water.

Hard contact lens cleaning and storage solutions formulated in accordance with this invention are hypotonic. These solutions are not intended to direct introduction in the eye, so tonicity adjustment is not important. The low level of salt ions in the solution of this invention helps preclude the accumulation of undesirable residues in contact lens storage kits. A more detailed description of this cleaning and germicidal composition for hard contact lenses is found in the above mentioned application Ser. No. 148,993 which is hereby incorporated by reference.

ln accordance with another aspect of the invention, a cleaning solution is provided for cleaning hydrophilic gel lenses and comprises 0.01 to 40% of a poly(ox yethylenej polytoxypropylene) block copolymer, a sufficient amount of a germicidal composition containing sorbic acid to preserve the sterility of the solution, a sufficient amount of at least one water soluble compatible salt to provide a solution having a tonicity compatible with human tear fluid, and a balance of water.

The block copolymers useful in this cleaning solution are the identical block copolymers that are used in the cleaning, storing and wetting solution for silicone lenses as described above and thus have the same com bination of physical and chemical properties that are described above in connection with the cleaning, storing and wetting solution for silicone lenses. Thus, the block copolymers have a molecular weight between about 1.900 and 15,500, and a water solubility in excess of about 10 grams per ml. Additionally, the block copolymers useful in the present invention must have a cloud point in 1% aqueous solution above about 30C, and a Foam Height in excess of 30mm.

The cleaning composition can contain from about 0.01 to 40% of the block copolymer and preferably contains 12 to 20% with 15% being presently preferred. A preferred block copolymer is sold under the trade mark Pluronic F-127 by the Wyandotte Chemical Corp.

The sorbic acid is incorporated into the cleaning composition hydrophilic gel lenses in an amount between 0.01 and 0.5% of the overall composition, and preferably in an amount of 0.1% to 0.2%. The sorbic acid has a bactericidal effect and importantly is not concentrated by the hydrophilic gel lenses, thus making it an ideal germicidal agent for use with hydrophilic gel lenses.

The hydrophilic gel lens cleaning composition preferably contains about 0.01-l.0% of a salt of ethylenediaminetetraacetic acid, such as disodium EDTA or trisodium EDTA. These salts serve as combination germicide and chelating agents. The sobic acid used in the cleaning composition has greater effectiveness at lower pH values and accordingly the cleaning composition is desirably maintained at a pH of 7 or below, with a pH of 6 being presently preferred. Preferably. disodium edetate is used in combination with the sorbic acid be cause trisodium edetate maintains the composition at a higher pH range. Disodium edetate is not concen trated by hydrophilic gel lenses and thus is a useful in gredient in cleaning solutions for such lenses. By itself, disodium edetate has a bacteriostatic effect. and in combination with sorbic acid provides a cleaning solution having good bactericidal properties.

A sufficient amount of at least one essentially neutral water-soluble compatible salt is incorporated in the hydrophilic gel lens cleaning solution of this invention to provide a tonicity compatible with human tear fluid. Preferably, the tonicity of the solution is isotonic with human serum and tear fluid, and thus has a tonicity of approximately 09%, although deviations of plus or minus 20% (OT/24.08% tonicity) can be made. Any greater deviation would cause undesirable differences in osmotic pressure between the natural fluids of the eye and the solution. Preferably, a mixture of sodium chloride and potassium chloride is used to achieve the desired tonicity.

A typical regimen for a hydrophilic gel lens contact wearer would call for cleaning the lenses immediately after they are removed from the eye with the cleaning composition of this invention, followed by water rinsing of the lenses. The lenses would then be subjected to boiling in normal saline in accordance with conventional procedures to asepticize them. The lenses would be hermetically kept in the normal saline until ready for use. The boiling fluid should contain a protective preservative to provide chemical resterilizing capacity in the event that the seal in the boiling container fails. The presence of a preservative should also be helpful if the container is opened to expose the lenses to non-sterile air for any significant period of time prior to wearing the lens.

The cleaning composition of this invention for hydrated gel lenses markedly improves the cleanliness and preserves the optical clarity of the lenses. Further,

studies indicate that patients who have previously experienced discomfort and red eyes associated with the wearing of their hydrophilic gel lenses have exhibited marked improvement when a cleaning step with the cleaner of this invention is incorporated in their daily care regimen.

Although the above cleaning composition is specifically formulated for use with hydrophilic gel lenses, the present invention has discovered that this composition can also be used as a cleaner for silicone rubber contact lenses and for hard polymethaerylate contact lenses. When used for these purposes, the tonicity of the solution can be varied over a wider range of 0.5-1 .8%. Although the silicone lens cleaning, storing, and wetting solution described above is satisfactory in obtaining cleaning of the silicone lenses, a still more effective procedure for the care of these lenses would be to first use the cleaning solution for the hydrophilic gel lenses, followed by water rinsing and then storage and wetting in the silicone lens cleaning, storing and wetting solution.

For a clearer understanding of the invention, specific examples of it are set forth below. These examples are merely illustrative and are not to be understood as limiting the scope and underlying principles of the invention in any way. All parts and percentages referred to in this specification and the appended claims are by weight in terms of unit volume of solution unless otherwise specifically indicated. Thus, a benzalkonium chloride content of 0.1 percent in the solution is equivalent to one gram of benzalkonium chloride per liter of solution.

The solution of this example wets flexible silicone contact lenses so that they can be inserted on the cor nea without eye irritation or tissue intolerance upon being taken out of the solution and without use of any other wetting solution.

This solution is tested clinically on six patients wearing flexible silicone lenses. The subjective response of these patients is that the solution is better than anything they had previously tried.

The germicidal and bactericidal activity of the cleaning and wetting solution of this example is tested against the following organisms:

(1) Staph. aureus (2) Strep. pyogenes (3) E. coli (4) Pseud. aeruginosa (5) C. albicans All tests are conducted in duplicate. Twenty four hour broth cultures of the organisms are centrifuged at 3,000 rpm for 20 minutes. The supernatant is decanted and the remaining pellet resuspended in phosphate buffered saline (PBS). Each bacterial suspension in the amount of 0.2 ml. is added to 3.8 ml. samples of the wetting and cleaning solution of this example and to 3.8 ml. samples of a control solution of PBS. The resulting suspensions represent a 1/20 dilution of the test reagent and are held at room temperature and assayed at 5, 30 and 60 minutes. The assay procedure consists of serially diluting by l0 fold the various bacterial suspension in Tryptic soy broth containing neutralizing buffer and Tween 80. The results of these tests are set forth in the following Table 1;

Table l Cleaning, Wetting and Storing Solution of this Example Time of Exposure of Organisms to Test Solution EXAMPLE 1 A cleaning, storing and wetting solution for flexible silicone contact lenses is prepared having the following composition:

Polyoxypropylene-polyoxyethylene This solution is rapidly germicidal on silicone contact lenses and these contact lenses can be stored indefinitely in the solution without the accumulation of deposits on the lenses.

Table 1 shows that the cleaning, storing and wetting solution is bactericidal even in the presence of large numbers of organisms.

The cleaning, storing and wetting solution of this example is also tested for eye irritancy. Two Silicon silicone rubber contact lenses (Mueller Welt Contact Lenses, Inc., Chicago, Ill) are placed in 5 ml. of the cleaning and wetting solution and soaked for 4 weeks at room temperature. At the end of the soaking period, the lenses are removed from the solution. This solution is then tested by the standard six-rabbit eye irritation test.

Six female albino New Zealand rabbits are used. Both eyes of each animal are examined before testing. The test solution is placed in one eye of each animal by gently pulling the lower lid away from the eyeball to form a cup into which the test substance is dropped. The lid is then gently held together for one second. The

other eye, remaining untreated, serves as a control. The dose for each rabbit is 0.l ml.

The eyes are examined and the grade of ocular reaction is recorded at 24, 48 and 72 hours. Reading of reactions is facilitated by the use of an ophthalmoscope. The reactions are scored by using the Illustrated Guide for Grading Eye Irritation by Hazardous Substances" as suggested in Section 191 l 2 of the Federal Hazardous Substances Act.

None of the rabbits tested show a positive reaction during the experimental period and thus the cleaning and wetting solution of this example is considered not to be an eye irritant.

In addition to being used as a cleaning, storing and wetting solution for flexible silicone lenses, the composition of this example is also an effective cleaning, storing and wetting solution for conventional hard polymethylmethacrylate lenses.

EXAMPLE 2 Another cleaning, storing and wetting solution for flexible silicone contact lenses in accordance with this invention is prepared in this example. The solution has the following composition:

Polyoxypropylene-polyoxyethylene condensate (Pluronic F427) 2.0% Benzalkonium chloride 0.0l 3% NaCl 0.9% Distilled Water I This composition is an effective germicidal, cleaning and wetting solution for flexible silicone contact lenses, and these lenses can be stored in it indefinitely.

EXAMPLE 3 Another cleaning, storing and wetting composition for flexible silicone contact lenses is prepared having the following composition:

Polyoxyethylene-polyoxypropylene 0.1% condensate (Pluronic F-l08) Thimerosal sodium 0.005% Disodium EDTA 0.05% KCI l.2% Deionized Water. 0.5. [00

This composition is an effective germicidal, cleaning and wetting solution for flexible silicone contact lenses, and these lenses can be stored in it indefinitely.

EXAMPLE 4 A cleaning composition for flexible hydrophilic gel contact lenses in accordance with this invention is prepared with the following ingredients:

Polyoxyethylene-polyoxypropylene condensate (Pluronic F427) 18% Sorbic Acid N.F.XIII O.l% Disodium EDTA 0.5% Sodium Chloride 0.65% Potassium Chloride 0.20% Deionized Water 0.5. 100

In addition this composition can be used for cleaning flexible silicone lenses and conventional hard polymethacrylate lenses.

EXAMPLE 5 A cleaning and cold sterilizing solution for hard methyl methacrylate contact lenses is prepared having the following composition:

Benzalkonium chloride 0.0l33% Trisodium ethylenediaminetctraacetatc 0.25 Polyoxypropylene-polyoxyethylcne 0.5 condensate (Pluronic F-68) Distilled Water. 0.8.

EXAMPLE 6 Another contact lens cleaning and storage solution for hard methyl methacrylate lenses in accordance with this invention is prepared in this example. The solution has the following composition:

Bcnzalkonium chloride 0.008 Trisodium ethylenediaminetetraacetate 0.3 Polyoxypropylene-polyoxyethylene condensate (Pluronic F-68) [.0 Distilled Water, 0.8. 100

This composition is an effective cleaning and germicidal storage solution for hard contact lenses, and such lenses can be stored in it indefinitely.

EXAMPLE 7 A gel-form cleaning composition for hard contact lenses is prepared having the following composition:

Benzalkonium chloride U.S.P. 0.025% Trisodium EDTA 0.25 Polyoxyethylenepolyoxypropylene condensate (Pluronic F-l27) 20.0 Deionized Water, 0.8. 100

The resulting composition is of gel consistency at room temperature (25C) and is physiologically tolerable. It produces no adverse sensation if inadvertently introduced directly into the eye.

Comparative cleaning tests are run using the gel cleaner of Example 7 and two commercial liquid contact lens cleaning compositions on lenses which have produced problems for wearers due to accumulated deposits on the lenses.

The two commercial cleaning compositions used in the tests are denoted Product 1 and Product 2. Each is known to contain a cleaning agent and water.

One hundred hard contact lens patients complaining of discomfort associated with their lenses are examined. The lenses are inspected with a 20 power magnifying lens for cleanliness, scratches, chips and warping.

The initial optical screening shows that 39 patients have scratched lenses. chipped lenses and other problems not related to lens cleanliness. Sixty-one patients have dirty lenses. In every instance where the lenses were dirty, the condition was about equal on both lenses. Of the 61 patients with dirty lenses. twentyseven have precipitated proteninaceous material adhering to the edges of their lenses, 31 have an oil material (probably from their use of oil base eye makeup) coating their lenses and three have a uniform deposit over the lenses which was not identified.

The cleaning efficacy of the new nonionic gel cleaner was compared with that of Product 1 and Product 2 on the 61 pairs of dirty lenses. Cleaning in each instance is accomplished by applying the cleaner, rubbing the lens gently between the fingers. and rinsing with water. In each instance, cleaning efficacy is determined by viewing the lens under power magnification after it is subjected to the cleaning technique.

The 31 right lenses dirty with an oily material are cleaned with lighter fluid since it is a good solvent for oils and is also a standard for laboratory contact lens cleaning. This procedure completely cleans two lenses.

The remaining 59 dirty lenses are then cleaned with Product 2, followed by Product 1. None of the lenses is adequately cleaned. In all instances there is some foreign residue remaining. The concentrated gel cleaner is then used on all these lenses. The gel cleaner removes the remaining foreign substances from all but two lenses. These lenses had to be repolished to remove the remaining foreign matter.

All the 61 left lenses are cleaned directly with the new gel cleaner. In all instances the left lenses are cleaned after the first treatment.

The most difficult lenses to clean are the lenses coated with an unidentified substance. Four ofthese six lenses are cleaned with the new gel cleaner while Products 1 and 2 both fail to clean these lenses satisfactorily.

The gel cleaner of this invention provides markedly superior cleaning results as compared to the two commercial products.

The invention in its broader aspects is not limited to the specific details shown and described, but departures may be made from such details within the scope of the accompanying claims without departing from the principles of the invention and without sacrificing its chief advantages.

What is claimed is:

l. A cleaning and storage solution for hard contact lenses consisting essentially of: from 0.002 to 0.2% of benzalkonium chloride for inhibiting microbial growth in the solution; from 0.01 to 2% trisodium ethylenediaminetetraacetate; from 0.1 to 10% of a physiologicallyacceptable nonionic surfactant selected from the group consisting of polyoxyethylene fatty acid ethers, polyoxyethylene fatty acid esters, and polyoxypropylenepolyoxyethylene block polymers; and water.

2. The composition of claim 1 wherein the pH of the composition is from greater than 7 to 10.

3. The composition of claim 1 in which the nonionic surfactant is a polyoxypropylene-polyoxyethylene block polymer having a molecular weight of from 1,000 to 15,000.

4. The composition of claim 1 which contains 0.002 to 0.03% benzalkonium chloride.

5. A gel cleaning composition for hard contact lenses consisting essentially of: from 0.002 to 0.2% of benzalkonium chloride for inhibiting microbial growth in the solution; from 0.01 to 2% trisodium ethylenediaminetetraacetate; from about 18 to 60% of a physiologically-acceptable nonionic surfactant selected from the group consisting of polyoxyethylene fatty acid ethers, polyoxyethylene fatty acid esters, and polyoxypropy1ene polyoxyethy1ene block polymers; and water.

6. The composition of claim 5 in which the nonionic surfactant is a polyoxypropylene-polyoxyethylene block polymer having a molecular weight of from 1,000 to 15,000.

7. The composition of claim 6 in which the concen tration of nonionic surfactant is about 20 percent and the composition is a gel.

8. The composition of claim 5 which contains 0002 to 0.03% benzalkonium chloride.

9. The composition of claim 8 which contains about 0.004 to 0.02% benzalkonium chloride.

10. The composition of claim 5 wherein the pH of the composition is from greater than 7 to 10.

11. A gel-form cleaning composition for hard contact lenses consisting essentially of 0.025% benzalkonium chloride; 0.25% trisodium ethylenediaminetetraacetate; 20% polyoxyethylene-polyoxypropylene block copolymer having a molecular weight of from 10,500 to 12,500; and purified water. 

1. A CLEANING AND STORAGE SOLUTION FOR HARD CONTACT LENSES CONSISTING ESSENTIALLY OF: FROM 0.002 TO 0.2% OF BENZALKONIUM CHLORIDE FOR INHIBITING MICROBIAL GROWTH IN THE SOLUTION; FROM 0.01 TO 2% TRISODIUM ETHYLENEDIAMINETETRAACETATE; FROM 0.1 TO 10% OF A PHISIOLOGICALLY-ACCEPTABLE NONIONIC SURFACTANT SELECTED FROM THE GROUP CONSISTING OF POLYOXYETHYLENE FATTY ACID ETHERS, POLYXYETHYLENE FATTY ACIDS ESTERS, AND POLYOXYPROPYLENE-POLYOXYETHYLENE BLOCK POLYMERS; AND WATER.
 2. The composition of claim 1 wherein the pH of the composition is from greater than 7 to
 10. 3. The composition of claim 1 in which the nonionic surfactant is a polyoxypropylene-polyoxyethylene block polymer having a molecular weight of from 1,000 to 15,000.
 4. The composition of claim 1 which contains 0.002 to 0.03% benzalkonium chloride.
 5. A gel cleaning composition for hard contact lenses consisting essentially of: from 0.002 to 0.2% of benzalkonium chloride for inhibiting microbial growth in the solution; from 0.01 to 2% trisodium ethylenediaminetetraacetate; from about 18 to 60% of a physiologically-acceptable nonionic surfactant selected from the group consisting of polyoxyethylene fatty acid ethers, polyoxyethylene fatty acid esters, and polyoxypropylene-polyoxyethylene block polymers; and water.
 6. The composition of claim 5 in which the nonionic surfactant is a polyoxypropylene-polyoxyethylene block polymer having a molecular weight of from 1,000 to 15,000.
 7. The composition of claim 6 in which the concentration of nonionic surfactant is about 20 percent and the composition is a gel.
 8. The composition of claim 5 which contains 0.002 to 0.03% benzalkonium chloride.
 9. The composition of claim 8 which contains about 0.004 to 0.02% benzalkonium chloride.
 10. The composition of claim 5 wherein the pH of the composition is from greater than 7 to
 10. 11. A gel-form cleaning composition for hard contact lenses consisting essentially of 0.025% benzalkonium chloride; 0.25% trisodium ethylenediaminetetraacetate; 20% polyoxyethylene-polyoxypropylene block copolymer having a molecular weight of from 10,500 to 12,500; and purified waTer. 